Memory organization method for a fuzzy logic controller and corresponding device

Abstract

A method for setting up the memory of an electronic controller operates using fuzzy logic, whereby predetermined membership functions f(m) of logic variables M, defined within a universe of discourse sampled in a finite number of points m, are subjected to inference operations basically configured by IF/THEN rules with at least one front preposition and at least one rear implication. The controller includes a central control unit provided with a memory section for storing predetermined values of the membership functions f(m) which appear in the front or IF part of the fuzzy rules and have a predetermined degree of truth or membership. This method provides for storing into the memory section only the values of those membership functions f(m) which have a value of the degree of membership other than zero at the points m of the universe of discourse.

What is claimed is: 
     
       1. A method for loading information into a memory section of an electronic controller which performs inference operations according to rules, each rule comprising at least one preposition and at least one implication, wherein a number of membership functions are defined for a finite number of points within a universe of discourse, the method comprising the steps of: providing values of the membership functions appearing in the preposition of at least one of the rules, each value being indicative of a degree of membership; and   storing in the memory section, for each of the finite number of points, the values of only those membership functions for the point which are not zero.   
     
     
       2. The method of claim 1, further comprising the step of determining which of the finite number of points has a largest number of non-zero values, and wherein the step of storing includes storing a memory word in the memory section, wherein a length of the memory word is dependent on the largest number of non-zero values. 
     
     
       3. The method of claim 2, further comprising the step of determining the length L of the memory word such that   L=nf(m)*(dim(G)+dim(f(m)), where     nf(m) is the largest number of non-zero values, dim(G) is a word size required to represent a value indicative of a degree of membership, and dim(f(m)) is a word size required to represent the number of the membership functions.   
     
     
       4. The method of claim 3, wherein the largest number of non-zero values is between one to five, inclusive. 
     
     
       5. The method of claim 4, wherein the largest number of non-zero values is three. 
     
     
       6. The method of claim 1, wherein the step of storing comprises storing, for each point in the finite number of points, a memory word comprising an indication of each of the membership functions with a non-zero value for the point and the non-zero value. 
     
     
       7. The method of claim 6, wherein the step of storing a memory word for a point comprises the step of storing the memory word for the point such that the memory word is retrievable by applying an indication of the point to the memory section. 
     
     
       8. An electronic controller, comprising: a central control unit which performs inference operations according to rules, each rule comprising at least one preposition and at least one implication, wherein a plurality of membership functions are defined for a finite number of points of a universe of discourse, each membership function having a value for each of the finite number of points, which value is indicative of a degree of membership, and wherein at least one of the rules has a preposition including one of the membership functions; and   a memory section for storing values of the membership functions wherein the memory section has a size defined by a number of nonzero values of the membership functions associated with a selected one of the finite number of points, the selected point having the largest number of nonzero values.   
     
     
       9. The electronic controller of claim 8, wherein a length L of a memory word of the memory section is dependent on the largest number of non-zero values. 
     
     
       10. The electronic controller of claim 9, wherein the length L of the memory word is   L=nf(m)*(dim(G)+dim(f(m)), where     nf(m) is the largest number of non-zero values, dim(G) is a word size required to represent a value indicative of a degree of membership, and dim(f(m)) is a word size required to represent the number of the membership functions.   
     
     
       11. The electronic controller of claim 9 or 10, wherein the number of non-zero values is between one to five, inclusive. 
     
     
       12. The electronic controller of claim 11, wherein the number of non-zero values is three. 
     
     
       13. An electronic controller, comprising: a central control unit which performs inference operations according to rules, each rule comprising at least one preposition and at least one implication, wherein a plurality of membership functions are defined for a finite number of points of a universe of discourse, each membership function having a value for each of the finite number of points, which value is indicative of a degree of membership, and wherein at least one of the rules has a preposition including one of the membership functions; and   a memory section for storing values of the membership functions wherein the memory section stores, for each point of the finite number of points, the values of only those membership functions of the point which are not zero.   
     
     
       14. The electronic controller of claim 13, wherein the memory section stores, for each point of the finite number of points, a memory word comprising an indication of the membership functions with non-zero values for the point and the non-zero values. 
     
     
       15. The electronic controller of claim 14, wherein the memory word for the point is stored in the memory section such that the memory word is retrievable by applying an indication of the point to an input of the memory section. 
     
     
       16. The electronic controller of claim 13, wherein the memory section has a size defined by one of the finite numbers of points having a largest number of non-zero values. 
     
     
       17. The electronic controller of claim 16, wherein a length L of a memory word of the memory section is dependent on the largest number of non-zero values. 
     
     
       18. The electronic controller of claim 17, wherein the length L of the memory word is L=nf(m)*(dim(G)+dim(f(m)), where nf(m) is the largest number of non-zero values, dim(G) is a word size required to represent a value indicative of a degree of membership, and dim(f(m)) is a word size required to represent the number of the membership functions. 
     
     
       19. The electronic controller of claim 17 or 18, wherein the largest number of non-zero values is between one to five, inclusive. 
     
     
       20. The electronic controller of claim 19, wherein the largest number of non-zero values is three. 
     
     
       21. A memory section for an electronic controller which performs inference operations according to rules, each rule comprising at least one preposition and at least one implication, wherein a membership function, defined for a finite number of points of a universe of discourse, appears in the preposition of at least one of the rules, the membership function having a value for each of the finite number of points, which value is indicative of a degree of membership, wherein the memory section stores for each point of the finite number of points the values of only those membership functions for the point which are not zero. 
     
     
       22. The memory section of claim 21 which stores, for each point of the finite number of points, a memory word comprising an indication of the membership functions with non-zero values for the point and the corresponding non-zero values. 
     
     
       23. The memory section of claim 22, wherein the memory word for the point is stored such that the memory word is retrievable by applying an indication of the point to an input of the memory section. 
     
     
       24. The memory section of claim 21 having a size defined by which point of the finite numbers of points has a largest number of non-zero values. 
     
     
       25. The memory section of claim 24, wherein a length L of a memory word of the memory section is dependent on the largest number of non-zero values. 
     
     
       26. The memory section of claim 25, wherein the length L of the memory word is L=nf(m)*(dim(G)+dim(f(m)), where nf(m) is the largest number of non-zero values, dim(G) is a word size required to represent a value indicative of a degree of membership, and dim(f(m)) is a word size required to represent the number of the membership functions. 
     
     
       27. The memory section of claim 25 or 26, wherein the largest number of non-zero values is between one to five, inclusive. 
     
     
       28. The memory section of claim 27, wherein the largest number of non-zero values is three. 
     
     
       29. A memory section for an electronic controller which performs inference operations according to rules, each rule comprising at least one preposition and at least one implication, wherein a membership function, defined for a finite number of points of a universe of discourse, appears in the preposition of at least one of the rules, the membership function having a value for each of the finite number of points, which value is indicative of a degree of membership, wherein the memory section has a size defined by a number of nonzero values of the membership functions associated with a selected one of the finite number of points, the selected point having the largest number of nonzero values. 
     
     
       30. The memory section of claim 29, wherein a length L of a memory word of the memory section is dependent on the largest number of non-zero values. 
     
     
       31. The memory section of claim 30, wherein the length L of the memory word is L=nf(m)*(dim(G)+dim(f(m)), where nf(m) is the largest number of non-zero values, dim(G) is a word size required to represent a value indicative of a degree of membership, and dim(f(m)) is a word size required to represent the number of the membership functions. 
     
     
       32. The memory section of claim 30 or 31, wherein the number of non-zero values is between one to five, inclusive. 
     
     
       33. The memory section of claim 32, wherein the number of non-zero values is three. 
     
     
       34. A method for using an electronic controller which includes a central control unit which performs inference operations according to rules, each rule comprising at least one preposition and at least one implication, wherein a plurality of membership functions are defined for a finite number of points of a universe of discourse, each membership function having a corresponding value for each of the finite number of points, which value is indicative of a degree of membership, and wherein at least one of the rules has a preposition including one of the membership functions, and a memory section for storing predetermined values of the membership functions wherein the memory section stores, for each of the finite number of points, an indication of and the value corresponding to only those membership functions for which the degree of membership of the point is not zero, the method comprising the steps of: receiving an input indicative of one of the finite number of points;   obtaining from the memory the predetermined non-zero values of the membership functions for the received point and identities of corresponding membership functions;   selecting a membership function; and   restoring effective values of the membership functions from the obtained non-zero values and identities to extract predetermined weights involved in the rules which configure the inference operations.   
     
     
       35. The method of claim 34, wherein the step of restoring comprises the steps of: comparing the selected membership function to the indications of the membership functions stored for the received point; and   outputting zero when an indication of the selected membership function is not stored for the received point.   
     
     
       36. The method of claim 34, wherein the step of restoring comprises a step of comparing bits of a part (w(f(m) i )) of the memory word output from the memory section related to the membership functions (f(m) i ) with bits of a reference word (w(f rif )) contained in a program memory in which the rules which configure the inference operations are stored. 
     
     
       37. The method of claim 36, wherein the step of comparing said part (w(f(m) i )) of the memory word output from the memory section with bits of said reference word (w(f rif )) from said program memory obeys the following logic relationship:   if w(f.sub.rif)=w(f(m).sub.i) then weight=value 1.sub.f(m)i, and       if w(f.sub.rif)≠w(f(m).sub.i) then weight=0,     wherein weight is a value selected during the step of restoring, and 1 f (m)i is a value corresponding to an i-th membership function where i is a non-negative integer.   
     
     
       38. An electronic controller, comprising: means for receiving an input which indicates one of a finite number of points;   a memory section for storing predetermined values of the membership functions wherein the memory section stores, for each of the finite number of points, an indication of and the value of only those membership functions for which the degree of membership of the point is not zero;   a calculating section for performing the fuzzy logic inference operations; and   a buffer section, between the memory section and the calculating section, for regenerating effective values of the membership functions to extract predetermined weights involved in the rules which configure the inference operations.   
     
     
       39. The electronic control device of claim 38, wherein the buffer section comprises a comparator having a first input for receiving an indication of a selected membership function from the central control unit and a second input connected to the output of the memory for receiving the indications of and the values of membership functions stored for the point indicated by the means for receiving and having an output which provides a zero output when the selected membership function is not indicated by the indications received from the memory. 
     
     
       40. An electronic control device of claim 38, wherein the buffer section comprises a program memory, in which all the rules for the inference operations are stored, and having an output indicative of a membership function; and a comparator, for comparing bits of a part of the memory word output from the memory section and related to the membership functions, with bits of a reference memory word contained in the program memory.   
     
     
       41. The electronic control device of claim 40, wherein the comparator is connected to the program memory through a micro-encoder which selects the reference words within the program memory. 
     
     
       42. The electronic control device of claim 40, wherein the comparator has inputs connected to respective outputs of the memory section and the program memory, and is connected to the input of the calculating section.